Electrical measuring instrument



June 17, 1930. w. HALLACK ELECTRICAL MEASURING INSTRUMENT F'iied Dec. 21, 1925 DISCHARGE CHARGE AM PERE5 Patented June 17, 1930 WILLIAM HALLACK, OF DEARBORN, IMIIIGHIt'iAlfl' ELECTRICAL Mms'onrNG INSTRUMENT Application filed December 21, 1925. Serialfio. 76,919.

This invention has for its object to simplify and render less expensive electrical measuring instruments, particularly ammeters of the type used on motor vehicles, and is concerned both with the mechanism of the device and the casing whereby it is enclosed.

As to the latter, it comprises a cup-shaped shell and a cover between which and the shell a'face plate or dial, preferably of celluloid or similar material, is directly clamped.

The instrument mechanism proper involves several new and desirable features, principally (1) a means for so intensifying the field of the conductor that the need for a coil is avoided, (2) the mounting of the pointer on the conductor, thus dispensing with a number of parts ordinarily used, and (3) a manner of mounting the magnet in the casing without the use of additional parts. Other features will be noted as the description proceeds.

' In the drawings, Fig. 1 is a front view of a preferred embodiment of the invention; Fig. 2 is a similar view, the shell cover and glass face being removed; and Figs. 3 and 4 are sectional views on lines 3-3 and 4-4 respectively of Fig. 2.

1 indicates a cup-shaped shell of brass, zinc or other suitable non-magnetic material, which with the associated shell cover2 and faceplate 3 carried by the latter make up the casing. 1 preferably arrange the forwardly turned annular flange of the member 1 within the closely fitting rearwardly turned flange of the cover and make it of such depth as to press on the face plate 3 when the parts are assembled, thus avoiding the necessity for retaining rings or other equivalent devices such as are ordinarily used. I also preferably make the face plate of celluloid (although glass may be used) and either ink or cover its inner surface with paper to provide an opaque field having a transparent slot 5, through which the pointer, hereinafter described, may be seen and read by reference to the graduated are 6.

WVithin the casing, which may be varied widely from the desirable construction shown, is a conductor or bus bar 10, preferably consisting of a substantially flat strip of metal of shape resembling the letter U. Internal ,currentflow, that is, whether charging or washer or washers 12 and external washers 13, together with terminal bolts 14 and nuts 15, serve to rigidly mount the conductor within the shell and to insulate it therefrom. For convenience in assembly,the heads 16 of the bolts may be flattened on their upper sideand held. from turning by means of forwardly turned end portions 17 formed on the corresponding legs of the conductor (Fig. Associated with the conductoris a permanent magnet 20 which in the construction shown is an open ring held in place within the shell by spring tension but which may be made in other suitable forms and held in place by other means. It will be observed that the 5 intermediate portion of the conductor lies along or in the more intense portion'of the magnetic field. The conductor is provided at the middle of its lower edge with a for wardly extending arm 21 having an upturned end portion 22. By positioning the magnet about the conductor and spacing it therefrom as shown, less tendency toward depolarization exists than wouldbe the case were the magnet placed in the more intense part of the field of the conductor.

Mounted between the conductor proper and the part 22 is a pivot 30 arranged perpendicular to the face of the instrument and carrying a pointer or needle 31 and a counterweight 32 therefor, both preferably of'nonmagnetic material; likewise an armature 83, preferably of soft steel, positioned in such manner as to hold the pointer, whenno current is flowing in the conductor, at the zero indicationon the dial. The armature is also in the field which exists about the intermediate portion of the conductor when current flows therein, it being understood that the lines of force in said latter field intersect the armature at substantially right angles to those of the permanent magnet, thereby causing deflection of the needle in one direction or the other dependent on the direction of discharging, when the instrument is applied to the electric system of an ordinary vehicle or the like. It will be noted that the movement of the needle counterweight 32 is limited by the portion 21 of the conductor, thereby preventing the pointer from contacting with the casing. Thus the insulation of the conductor is the only insulation needed.

Manifestly the construction thus far described has the merit of simplicity and low cost as compared with ammeters in ordinary use, but it would not ordinarily be sufficiently sensitive for the purpose. I therefore mount upon the 'con'dluctor'at a point opposite the armature a 'soft iron" pole piece"4O which preferably lies flat against that side ofthe conductor farthest from the armature and which serves to concentrate the lines of force and thereby intensify the ficldnof the'condu'ctor where it acts on the armature. The pole piece may be secured to theconductor inany suitable way suchas soldering or by prongs 41 beii'tj'overalong the'uppe'r and lower edges of thecond ictor'as shown.

' will'be netedthatthe terminal bolts or binding posts are" arranged substantially ibngaeommon diameterfof the shell .1 thus the intermediate portion of the conductor "and the 'pi'v'otfon which the pointer is supported are located wellftoward the circumference of the shell, thereby "permitting the use of a needlean'diassociated scale of proper length,

whileatthe same timethe posts are separated from each other sufii'cientlytoafford ease of connection of-the wiring;

rc'laimw I 1." electrical mea'suring instrument comprising a conductor, means for establishin fa megneticfiel'd aboutsaid conductor at suh'tantially right angles'to thefield' resultingfrom the new of current ,therethrough, a

'pi'votally mounted armature supported solely by said conductor in" the intersection of saidfields and adapted to' be deflected in a direction depending "uponIthe direction of flow of fsaid c'urrent,land a pole piece'fixedto said conductor" L and supported thereby in position to intensify the magneticufield to whichfthe armature is subjected i' Y 'QYA'n "electricalf measuring" instrument comprising a permanent magnet, a conductor intersecting the field of? said magnet and I havin'g' a forwardly and upwardly extending portion, a spindle havingits ends supported re'spectivelyensaid portionand on the adj a cent remaining partof said conductor, an armaturecarrieu by said spindle :andibeing subject to the fi'eld'of the magnet and also to the field f existi'ng about the conductor when ourrentjis iflo'w'ing therein whereby the armatur'e is deflected in one direction or the other depending'jon the direction of said current, and a polepiece fixe'dtofs'aid conductor and supported thereby j ini positio'n to intensify the magneticffie l'd to which the s armature is subjected; 7 1 v i i agar electrical measuring instrument comprising a casing substantially circular'infcr oss section, a substantially urshaped conductor insulated from the casing, binding posts located on a common diameter of the casing and co-acting with the upper ends of the limbs of said conductor to support the latter, a permanent magnet in the casing with the more intense portion of its field substantially on the line of the mid portion of said conductor, and an armature mounted in said field to swing about an axis substantially parallel to that ofthe casing, thefdirection of movementof the armature being dependent on the direction of flow of current in said conductor. 1 a

4. An electrical measuring instrument comprising acup shaped shell of non-magnetic material, a permanent magnet of the open ring'ty'pe conforming to the inner wall flow of current the latter.

;5. ,An electr cal instrument compr sing a uppo t. a n -P a substan al y U-sha'ped conductor carriedtherebv and-insulated therefrom, binding posts connected tgthe respective end portions of saidconductor, a' permanent magnet, means including an' armature andl a*pointer supportedby saidcon ductor and influenced by themagnet and by the "magnetic field resulting from flow of current in said conductorto indicate the direction of said lfiow. A

'6.. An" electrical measuring instrument comprising substantially U-shaped conductor the li'mbs 'ofwhich lie' substantially in the same planefa permanent magnet surrounding the conductor and spaced therefrom and;

having'the more intense po rtion of its field about and'substantially parallel to the mid:

portion "of the coductor, a pole piece fixed to the mid-portion ofthe conductor, and a pivoted armature in said intenseportion of the fieldof themagnet.

"7; An electrical vmeasuring instrument comprising a substantially U -shaped 6on du'ctor' theilimbs of lwhich lie substantially in the same plane, a I permanent magnet' arranged with the more intense portion ofits field about the mid-portion ofthe conductor and substantially parallel ,thereto, a pole piece fixed to the mid-portion of the conductor and positioned ,closely along one face thereof, and an armature on the opposite-side of said conductor in the field of saidmagnet' and also in the field o f the conductor when current flows therein.

8. An electr cal ,.measur1ng instrument comprising acasing substantially circular in.

cross section, a substantially 1 U-shaped conductor insulated from the casing, binding postscdactingiwith the upper ends of the limbsof said conductor to support the'latter, a permanent magnet in the casing with the more intense portion of its field substantiall on the line of the mid portion of said con uctor, and an armature mounted in said field to swing about an axis substantially parallel to that of the casing, the direction of movement of the armature being dependent on the direction of flow of current in said conductor.

9. An electrical measuring instrument comprising a casing forming a substantially cylindrical wall, a permanent magnet of the open-ring type within said Wall, said magnet being so constructed and arranged that when inserted in the casing it expands into engagement with said wall whereby the magnet is held in place within said casing.

In testimony whereof I afiix my signature.

WILLIAM HALLACK. 

